Pavement.



. No Drawing.

COMPANY, A CORPORATION OF ARIZONA.

PAVEMENT.

JLQQULGL To all whom it may concern:

Be it known that I, MICHAEL A. POPKESS, a citizen of the United States, residing at Kansas City, in the .county of Jackson and State of Missouri, have invented new and useful Improvements in Pavements, of which the following is a specification.

The present invention consists in a pavement, the main ingredient of which is a material which has heretofore been considered quite unsuitable for that purpose.

There exist in most localities, deposits of sand and gravel or stony fragments mixed with earthy material; dirty sand and gravel orstony matter in a more or less disintegrated state, such as is called weathered rock. Such materials, if mixed, in their natural state, with bitumen, do not result in a durable'qpavement. The reason is that the fine or earthy material forms a coating or shell around and adherent to the larger stony particles, which coating or shell prevents the bitumen from coming into actual contact with said stony particles and, therefore, from cementing them together.

Consequently, such deposits have never been considered as suitable for use,-in their natural condition, as an ingredient of as phaltic paving material, and, therefore, present day asphalt pavements are required to consist of clean, hard, sharp particles of graded sizes. The use of dirty material is not allowed.

Whereattempts have been made to use deposits in connection with hot asphalt, such as described above, the plasticity and colloidal qualities of the earthy material were destroyed, owing to the high temperatures used, whereby the clayey material was caused to flocculate or form lumpswhich would absorb water but not the bituminous binder.

The sand and gravel particles, thus coated with the agglutinated earthy material, frac- Specification of Letters Patent. f Patent gfl Nil a1. 27 1917 Application filed April 21, 1916. Serial No. 92,704. I

for this reason that round particles such as a gravel are not considered as satisfactory as broken stone. Clean, hard, sharp and irregular particles are demanded, the idea in this type of pavement being to have the aggregate support the trafiic by the stony partlcles resting on and locking with each other, the bitumen merely cementing said particles together.

In actual construction work where large quantities of different sized materials are used, the interlocking of the different sizes of'n'laterial is usually imperfectly attained on account of the fact that in handling and depositing on a road the large particles separate more or less from the fine particles and the different sizes tend to segregate into clumps in the mixing thereof, which pre vents the interlocking and close compacting action' or effect. The large interstlces so formed fill with lakes of asphalt which causes the pavement to soften very much in hot Weather.

The softening quality of these pavements is the cause, to a large extent, of the production of holes; it also causes creeping,

which makes the pavement uneven. and wavy; Also, the gradual crushing of the mineral aggregate in asphaltic pavements, as ordinarily constructed, produces mineral particles which are not coated with bitumen, thus destroying the cementation and allowing the pavement to erode and wear into I holes.

When the sheet asphalt or as haltic concrete pavement becomes hot, t e bitumen liquifies and ceases to act as a cement and its only "alue then is that it partially Waterproofs the mineral aggregate, to the extent that it fills part of the large voids with too I much bitumen and the small voids with too little. As a result, all of the load on the surface must be borne by the mineral aggregate, which transfers the load directly downward to the base. Because of the lack of tensile strength in the mineral aggregate -which constitutes the wearing surface a rigid base of concrete, or the like, is considered necessary.

Heretofore, in making bituminous pavements composed of a mineral aggregate and asphalt, the high temperatures used in heating the aggregate preparatory to mixing it with the asphalt, which was necessarily a hard asphalt of low penetration, tended to coke the latter, which therefore lost its cementing property to a corresponding extent, causing the pavement to disintegrate andthe formation of holes therein.

The present pavement is a modification of that covered by my Patent No. 1,008,433, and was conceived or discovered in the experimental use of the machine which is dis-' treated according to the process of my said.

patent, tests were made with earthy material such as described above, containing more or less gravel, dirty sand, disintegrated rock and the like, Naturally, the larger particles did not pass through the screen but were delivered out at the rear end thereof, and

were then mixed with the composition of dust and binder. These tests demonstrated that by the action of the pulverizer and the screen and the heat, the said solid stony particles had been thoroughly cleaned from all adhering -dirt and, indeed, were fractured and polished, and that, in that condition, the mixture of binder and earth would adhere to and coat them, giving a product satisfactoryv for paving. This product, consisting of cleaned stony particles, and of the combined earthy dust and asphalt, after being compacted, either to form a pavement in situ or into blocks, was practically as coherent and possessed almost as much tensile strength as my previous product made from earthymaterial substantially free from sand, gravel and stone.

With more energetic pulverization than that just described, the coarser, stony particles may be broken or pulverized further,

even to the extent of making dust. And I have found that the rock or stone dust so formed when used in conjunction with the natural fine material of the soil also makes a satisfactory pavement. This fine dust may also be used alone with bitumen as disclosed and claimed in my application Serial No. 90,244, filed'April 10, 1916.

In the present embodiment of my invention however the pavement is composed of a mixture of clean or cleaned sand and gravel or rock fragments with the stated earth-bitumen composition. This pavement may have the coarse material present in about the proportion in which it is found in the soil used for road-making or in another proportion. In the former event, ordinarily each of the coarser rock fragments or gravel bodies is spaced from and united to the others by intervening layers of the earth bitumen composition; the several coarse bodies are embedded in the composition. Sometimes, where the proportion of coarse stuff is greater, the composition may act merely to fill voids and cement the bodies together; the structure then being more nearly analogous to the ordinary pavement save that in lieu of using as halt for cementing and void filling I am usmg the stated earthbitumen composition.

In the present invention however I contemplate more specifically a composition in which the stony or rocky matter is present merely as a" filler and the body of the composition is made up of the stated asphaltdust material. In this material I employ such a proportion of asphalt as will render it non-flowing. The particular proportion depends mainly upon the particular character of the dust and somewhat upon the character of. the asphalt. Artificially pro; 'duced dusts, such as those obtained by comminuting stony matters of all kinds, as a rule, with ordinary methods of production, are not as fine as the particles naturally existing in clayey soil; and the finer the particle the more asphalt is needed, or can be incorporated, without making the composition exhibit free asphalt even under summer temperatures. With clayey soils this proportion which can be present and still have the mixture non-flowing is therefore somewhat greater than with stony dust. With clayey dusts from silt or earth, as a rule, the proportion of dust must be over 55 per cent. and that of asphalt less than 45 per cent.

Obviously, in the operation of pulverizing such rotten stone, dirty sand and gravel, or disintegrated rock, not only will the earthy material, soil, loam or clay, be reduced to dust but some at least, if not all, of the stone, rock, sand and gravel will also be pulverized to dust, so that the wear resisting and traffic supporting ingredient of the pavement will consist of dust, made from any or all of said constituents, mixed with asphalt, while the filler may consist of the stony material which is not pulverized, or of clean sand, gravel or rock obtained elsewhere, the amount of filler used varying according to conditions and requirements but not exceeding 67% of the final pavement.

The present pavement presents several advantages, one of which is the fact that material can be used which is found nearly everywhere and has'heretofore had no commercial value as an ingredient of a pavement; another is that the gravel and stony particles, acting as" a filler, reduce the amount of bituminous binder required, and therefore the cost, where paving specifications call for a cheaper grade of pavement.

Decomposed and disintegrated earthy material of clayey nature, if not heated sufficiently to cause it to lose its plasticity and colloidal qualities, when mixed with the bitumen, completely fills and even enlarges the natural voids and acts as a cushion between the clean and fractured solid particles and constitutes itself a malleable wearing material, which will withstand the hardest traffic without fracture or disintegration, and which not only binds together the large stony particles, but actually gives protection to such particles from the grinding effects of traffic. Heretofore, the sand, gravel and rock, called the mineral aggregate, have been considered to be the wearing material of pavements of the kind described. EX- perience however has shown that such aggregate constitutes in reality a very poor wearing material when unsupported by a wear resisting binder, such as that described and claimed herein, because it rapidly fractures'and wears away under the conditions of modern traflic, which demand a difierent pavement from that which was fairly satisfactory under old traffic conditions.

I have also found that, when the hard particles crack and grind away, or come out of the surface of my pavement, the wear resisting substance, consisting of bitumen and earthy material, will actually iron out and fill the void left by the stony particle, so that, eventually, the wearing surface comes to consist entirely of the wear "resisting binder. The sand and gravel particles act more as a filler than as a wearing aggregate, and their main function is that of reducing the amount of bitumen required. Furthermore, the present pavement requires no grading or sizing of the mineral aggregate because its stability does not depend upon the interlocking of the particles of. stony material. The bituminized earth binder does not flow at any temperature, conse quently the pavement will not creep or become soft and wavy, or work into ruts under to bitumen than any other type of bituminous pavement containing sand, gravel and stone.

In cases where the natural earth does not contain the amount of sand, gravel, or crushed rock required or desired, it is obvious that more can be added, or even other mineral substances, such as slag, cement or the like, and it will also be obvious that naturally clean sand and gravel can be used without subjecting it to a cleaning treatment, and that such treatment, when necessary, may be performed in any other suitable wa Finalfy, the small amount of organic mat ter, which is usually present in earthy deposits, in no way injures the final product, when it is thoroughly dried out.

It will be seen from the above that an essential feature of this pavement, and one that distinguishes it from ordinary sand-asphalt or cement pavements, is that it does not depend-for its stability on the interlocking of the pieces of mineral aggregate, so that no grading according to size is necessary, and that, in the binder, the proportion of fine material or dust to the asphalt is much greater than ever heretofore used, whereby the latter is prevented from flowing. I have found that it is practically necessary that the binder should contain at least 70 per cent. of fine dust, and not over 30 per cent. of asphalt where a high penetration asphalt is used, and the mineral aggregate should not constitute more than twothirds of the total pavement material, and will frequently be much less than that. Practical experiments have shown, however, that by using a low penetration asphalt, the proportion of the fine dustw may be slightly less than 70 per cent, or as low as 65 per cent.

What I claim is 1. A pavement, composed of a wear-resisting and traffic-supporting mixture of finely disintegrated earthy material impregnated with not less than 14 per cent. and not more than 25per cent. of bitumen, and a or clay, reduced to a fine pow er and intimately mixed with not more than 35 per cent. of low penetration asphalt, and a filler consisting of a coarser mineral aggregate embedded therein, the whole being compacted under pressure.

3. A pavement, comprising the combination of a traffic-supporting and wear-resisting mass composed of absorbent earth ma- 'terial, reduced to dust and impregnate terial, reduced to dust and impregnate with bitumen, and a filler consisting of coarser mineral particles embedded-therein, substantially all of" which are separated from each other thereby, the whole being compacted under pressure.

4. A pavement, comprising the combination of a traflie supporting and wear-resist- .ing mass composed of absorbent earth ma- (l with not less than 14 per cent. and not more than per cent. of bitumen, and a filler of coarser mineral particles embedded therein, substantially all of which are separated from each other thereby, the whole being compacted under pressure.

5. A pavement, comprising the combina- 7 tion of a traflic-supporting and wear-resisting mass'composed of ordinary soil, loam or clay, dried and pulverized and intimately mixed with not-less than 17 per cent. and not more than 30 per cent. of bitumen, and a filler of coarser mineral particles embedded therein, substantially all of which are separated from 'each other thereby, the whole being compacted under pressure.

6. A pavement, comprising a pressure and wear resisting mass consisting of finely disintegrated earthy material, free from moisture. and intimately mixed with bit imen, in combination with a filler consisting of particles of sand or gravel embedded therein and separated from each other thereby, the Whole being compacted under pressure.

7 A pavement, comprising a pressure and Wear resisting mass, consisting of finely disintegrated earthy material intimately mixed with not more than 30 per cent. of bitumen, in combination with larger particles of filling material embedded therein and surrounded thereby, the whole being compacted under pressure.

8. A pavement, comprising a traflic supporting and wear resisting mass, composed solely of asphalt containing not less than 70 per cent. of finely divided earthy material, intimately mixed with a clean mineral aggregate of sand, gravel or crushed 'rock,

the mixture being spread and compacted on the surface to be paved. I

9. A pavement, comprising a pressure and wear resisting mass, composed of asphalt and fine dust intimately mixed together, in combination with a filler consisting of particles of sand, gravel or the like, surrounded by and embedded in said mass, the whole being compacted by pressure.

10. A pavement consisting of a plastic mixture of dust and asphalt, constituting the main wear-resisting and trifle-supporting ingredient, the proportion of dust to asphalt.

being at least as sixty-five to thirty-five, and a filler of sand, gravel, broken stone, or the like disseminated through said mixture, the whole being subjected to pressure.

11. A pavement composed of two elements viz.a binder and a 'filler, the former constituting the wear-resisting and traflic-supporting element and consisting of a mixture of not more than thirty-five per cent. of asphalt and at least sixty-five per cent. of fine dust, and the filler consisting of more or less finelydivided mineral particles, surrounded by and incorporated with said binder element, the whole subjected to pressure.

12. A pavement comprising, as the main wear resisting and traflic supporting component, an intimate mixture of asphalt, and the clayey or earthy portion of ordinary soil; said pavement also comprising the natural sand or gravel, disintegrated rock and the like of such soil in a clean condition.

13. A pavement comprising, as the main wear resisting and traflic supporting component, an intimate mixture of not more than 35 per cent. of asphalt and not less than per cent. of clayey or earthy matter from disintegrated natural soil, and also comprising a filler of cleaned stony particles, substantially all of which are surrounded and separated from each other by said mixture, said filler comprising not more than twothirds of the total pavement.

14. A pavement, consisting of two ingredients, one comprising at least one-third of the total and composed of an intimate mixture of mechanically pulverized dust and asphalt, and the other comprising not more than two-thirds of the total and composed of clean stony particles embedded in and 10 pulverized t0 fine dust, and a filler consist- 'ing of clean stony particles, embedded in and surrounded by said mass.

16. A pavement comprising a wear resisting and traffic supporting mass composed solely of a non-flowing mixture of asphalt and dust, in combination with a filler, constituting not more than two-thirds of the total and composed of clean particles of stone, sand, gravel, or the like, embedded in and substantially all surrounded by said mixture.

17. A pavement, composed of at least 20 per cent. of dust which will pass a 200 mesh screen, and of at least 12 per cent. of asphalt, combined with a filler of hard stony particles embedded in said mixture and substantially all of which are surrounded by and separated from each other thereby.

mao eei 18. A pavement, composed of at least 30 per cent. of dust which will pass a 100 mesh screen, and of at least 13 per cent. of asphalt, combined with a filler of hard stony particles embedded in said mixture and substantially all of which are surrounded by and separatedfrom each other thereby.

19. A pavement comprising a body of a composition of natural mineral matter in a dust like condition and asphalt in such relative proportions as to render such composition substantially non-flowing even under summer heat and a filler of coarser mineral matter carried by and embedded in such composition.

20. A pavement comprising a body of a composition of natural mineral matter in a dust like condition and. asphalt in such relative proportions as to render such composition substantially non-flowing even under summer heat and a filler of sand or gravel carried by and embedded in such composi tion.

In testimony whereof I have hereunto set my hand.

MICHAEL A. POPKESS. 

